P53, bcl-2 and bax immunoreactivity as predictors of response and outcome after chemotherapy for metastatic germ cell testicular tumours

Is Autophagy Always a Barrier to Cisplatin Therapy?

Cisplatin has long been a first-line chemotherapeutic agent in the treatment of cancer, largely for solid tumors. During the course of the past two decades, autophagy has been identified in response to cancer treatments and almost uniformly detected in studies involving cisplatin. There has been increasing recognition of autophagy as a critical factor affecting tumor cell death and tumor chemoresistance. In this review and commentary, we introduce four mechanisms of resistance to cisplatin followed by a discussion of the factors that affect the role of autophagy in cisplatin-sensitive and resistant cells and explore the two-sided outcomes that occur when autophagy inhibitors are combined with cisplatin. Our goal is to analyze the potential for the combinatorial use of cisplatin and autophagy inhibitors in the clinic.

Cisplatin Resistance in Testicular Germ Cell Tumors: Current Challenges from Various Perspectives

Testicular germ cell tumors share a marked sensitivity to cisplatin, contributing to their overall good prognosis. However, a subset of patients develop resistance to platinum-based treatments, by still-elusive mechanisms, experiencing poor quality of life due to multiple (often ineffective) interventions and, eventually, dying from disease. Currently, there is a lack of defined treatment opportunities for these patients that tackle the mechanism(s) underlying the emergence of resistance. Herein, we aim to provide a multifaceted overview of cisplatin resistance in testicular germ cell tumors, from the clinical perspective, to the pathobiology (including mechanisms contributing to induction of the resistant phenotype), to experimental models available for studying this occurrence. We provide a systematic summary of pre-target, on-target, post-target, and off-target mechanisms putatively involved in cisplatin resistance, providing data from preclinical studies and from those attempting validation in clinical samples, including those exploring specific alterations as therapeutic targets, some of them included in ongoing clinical trials. We briefly discuss the specificities of resistance related to teratoma (differentiated) phenotype, including the phenomena of growing teratoma syndrome and development of somatic-type malignancy. Cisplatin resistance is most likely multifactorial, and a combination of therapeutic strategies will most likely produce the best clinical benefit.

Clinical applications of recent molecular advances in urologic malignancies: no longer chasing a "mirage"?

As our understanding of the molecular events leading to the development and progression of genitourologic malignancies, new markers of detection, prognostication, and therapy prediction can be exploited in the management of these prevalent tumors. The current review discusses the recent advances in prostate, bladder, renal, and testicular neoplasms that are pertinent to the anatomic pathologist.

Molecular mechanisms behind the resistance of cisplatin in germ cell tumours

Cisplatin has been one of the principal chemotherapy agents for the last 30 years and is still used widely in the treatment of testicular, ovarian, lung, head and neck, bladder and several other tumours. Resistance to chemotherapeutic agents is a major obstacle for successful treatment. Treatment effect on germ cell tumours (GCTs) is more successful than in adults suffering from almost any other solid tumour, but resistance still appears in 20% of patients with metastatic disease. However, because of the young age of patients and few data regarding the process of becoming resistant, this situation is still a challenge. In this review we are going to analyse the published literature on cisplatin resistance in GCTs and explain the initiatives that the Spanish Germ Cell Cancer Group (GG) is taking to try to elucidate the molecular mechanisms behind this process.

Why does cytotoxic chemotherapy cure only some cancers?

Despite frequent responses to chemotherapy, curative treatment remains elusive for the majority of patients with metastatic solid tumors. By contrast, in testicular cancer, gestational choriocarcinoma, Hodgkin disease and high-grade lymphomas, chemotherapy is routinely curative, even for patients who present with widely disseminated disease. In the common advanced cancers, however, over 40 years of cytotoxic drug development has brought no significant change in cure rates. One interpretation is that the intrinsic properties of the malignancies themselves, rather than the qualities of individual drugs or combination therapies, are primarily responsible for their curability with chemotherapy. We suggest that the curability of these malignancies results from an intrinsic 'locked-in' state of sensitivity to proapoptotic stresses in these cells. A common property of such curable malignancies is that they arise from cells that undergo major genetic rearrangements or recombination as part of their normal physiology. The absence of further genetic and epigenetic changes in genes that regulate apoptosis, DNA repair and senescence allows these cells to maintain their intrinsic sensitivity to chemotherapy. This process allows the cells, when challenged with chemotherapy, to undergo the natural apoptotic pathways that contribute to their intrinsic qualities of chemosensitivity and high curability.

Chromosomes, genes, and development of testicular germ cell tumors

A literature review found 265 articles on testicular germ cell tumors (TGCTs) detailing the copy number of chromosomal regions and expression of 245 genes. An initial precursor stage, intratubular germ cell neoplasia (IGCN), is characterized by triploidization and an upregulation of KIT, ALPP, CCDN2, and ZNF354A, and a downregulation of CDKN2D. TGCT regularly have a series of chromosomal aberrations: a decrease in copy number at 4q21 approximately qter and 5q14 approximately qter; an increase at 7p21 approximately pter, 7q21 approximately q33, and 8q12 approximately q23 (especially high increase in seminoma); a decrease at 11p11 approximately p15 and 11q14 approximately q24; an increase at 12p11 approximately pter; a decrease at 13q14 approximately q31; an increase of 17q11 approximately q21 (only for nonseminoma); a decrease of 18q12 approximately qter; and an increase at 21q21 approximately qter, 22q11 approximately qter (only for seminoma), and Xq. Macroscopically overt TGCT is associated with a characteristic series of abnormalities in the retinoblastoma pathway including upregulation of cyclin D2 and p27 and downregulation of RB1 and the cyclin-dependent kinase inhibitors p16, p18, p19, and p21. TGCT thus has a synergistic pattern in gene expressions of the retinoblastoma pathway that is rare in other malignancies.

Towards an understanding of the biological basis of response to cisplatin-based chemotherapy in germ-cell tumors

Chemotherapy is far more successful in young male patients with germ-cell tumors than in adults suffering from almost any other solid tumor. Various attempts have been made to understand the sensitivity of these tumors towards cisplatin-based chemotherapy; however, to date no explanation has been generally accepted. Recent data underline the need to seek further explanations, other than the previously postulated high intrinsic level of wild-type P53 protein, for the exquisite curability of germ-cell tumors. In this regard, the DNA repair pathways, in particular the DNA mismatch repair and nucleotide excision repair pathways, have received attention. This review summarizes the data currently available on the cellular basis for chemotherapy response in these tumors by systematically following cisplatin-presumably the most active drug in the treatment of this disease-on its course from entering the cell to the execution of apoptosis. The emerging picture points towards a multifactorial explanation for the unique chemosensitivity of germ-cell tumors, including a lack of export pumps, an inability to detoxify cisplatin and repair the respective DNA damage, and an intact apoptotic cascade not disturbed by anti-apoptotic stimuli. Even though no uniform pattern of relevant resistance factors has been identified in patients suffering from refractory disease, a significant number of these cases may be caused by defects in the DNA mismatch repair pathway.

Tumor p53 status and response to topoisomerase II inhibitors

It is thought that when tumor cells are treated with anticancer drugs, they die through the apoptotic pathway and that cell resistance to cancer chemotherapy is mainly a resistance to apoptosis commitment. p53 is not functional in nearly half of the tumors examined and because of its involvement (directly or through its target genes) in the apoptotic pathway, drug resistance to chemotherapy has been largely attributed to the status of this "tumor suppressor protein". Topoisomerase II (topo II) inhibitors are widely used not only as single agents, but also in the majority of combination treatment protocols for hematologic malignancies and solid tumors. The relationship between p53 and topo II raises many questions about basic regulatory, biochemical, structural and functional characteristics that could be different in cells in different tissues, and most importantly, between different tumor cell types and their normal tissue counterpart. Understanding these relationships may lead to strategies for chemotherapy optimization and further precision targeting of tumor cells in order to avoid drug resistance and thereby chemotherapy failure.

The future of therapy for nonseminomatous germ cell tumors

This article has reviewed recent advances in understanding the molecular mechanisms of germ cell transformation, germ cell tumor differentiation, and germ cell tumor chemotherapy sensitivity and resistance. Future developments should include the following: The use of high-throughput techniques to assess tumor biology and evaluate new markers will allow more sophisticated assessment of prognosis. Future therapy will use oligonucleotide chips, perhaps specific to germ cell tumors or gene products associated with drug resistance, to assign treatment (radiation, RPLND, chemotherapy). The pathways associated with metastases and resistance will either replace or amplify the current risk algorithms and the clinician's ability to select therapy. The same high-throughput techniques will identify critical molecules and pathways, providing new specific treatment targets. Cell cycle-specific targets are an ideal focus of study, because genes abrogating normal cell cycle control and promoting germ cell tumorigenesis are increasingly identified. In germ cell tumors, CCND2 and KIT are open to study. Molecular and genetic markers of differentiation are additional resistance markers and should be a focus of study. In this context, the treatment of malignant transformation and the prediction of teratoma at metastatic sites will take on a greater importance. Over the past 2 decades, the treatment of germ cell tumors has become well-defined. Further improvement requires that investigators find new markers corresponding to tumor phenotype. This achievement will prevent unnecessary treatment in patients destined to have a favorable outcome, and will target biologically unfavorable or resistant disease for new therapy developed specifically to target the molecular or genetic defects that disrupt normal cell cycle control.

Bax, Bcl-2, fas and Fas-L antigen expression in human seminoma: correlation with the apoptotic index

Apoptosis plays a crucial role in the regulation of spermatogenesis in male germ cells and is, at least in part, modulated by Bcl-2, Bax, and the Fas pathway. Seminomas have a favourable outcome and respond to radio-/chemotherapy with an increased rate of apoptosis. The expression of Bax, Bcl-2, Fas and Fas-ligand (Fas-L) in human seminoma was evaluated and correlated with the apoptotic index. Twenty-nine classical seminomas were examined by immunohistochemistry and Western blotting using antibodies against Bax, Bcl-2, Fas and Fas-L. Apoptosis was detected by in-situ end-labeling of fragmented DNA and the apoptotic index (AI) was determined. Expression of Fas was found in 26 (89.7%) of Fas-L in 24 seminomas (82.2%); none of the tumours expressed Bcl-2. No correlation between the AI and Fas, Fas-L or Bcl-2 expression was found. Bax was demonstrated in 20/29 tumours (69%). Bax-positive tumours showed an increased AI of 4.75 +/- 2.38% in contrast to 2.60 +/- 1.23% of the Bax-negative tumours (P = 0.002). The number of Bax-positive tumour cells and apoptotic cells revealed a significant correlation using chi2-test (P = 0.04) and linear regression (r = 0.54, P = 0.001). Therefore, Bax seems to play a determinant role in the modulation of apoptosis in human seminoma that may be linked to a favourable outcome.

Important factors in the diagnosis and primary staging of testicular tumours

PURPOSE OF REVIEW

In the present review we outline the use of different staging methods and highlight future possibilities in the management of testicular germ cell cancer.

RECENT FINDINGS

The 5-year survival for testicular cancer has improved dramatically over the past 30 years, with cure rates approaching 95%. This success is attributed to the appropriate integration of effective treatments and staging modalities. Staging currently represents the cornerstone on which treatment is based. Because most patients will be cured, attention has shifted toward reducing morbidity of treatment while maintaining high cure rates. This implies that staging must be accurate before any change to the treatment regimen can be instituted.

SUMMARY

Effective management of testicular germ cell cancer continues to pose a major challenge. Early and accurate diagnosis is very important because it will influence the choice of treatment and thus may impact on prognosis.

Clinical stage I nonseminomatous testicular germ-cell tumors: surgery or watchful waiting, still an issue?

PURPOSE OF REVIEW

The optimal management for clinical stage I nonseminomatous testicular germ-cell tumors is still a subject open to controversy. The main options of standard-care surveillance and primary nerve-sparing retroperitoneal lymph node dissection result in the same high cure rate (close to 100%). It is the purpose, here, to present a critical review of recent developments concerning primary therapy for clinical stage I nonseminomatous testicular germ-cell tumors and to identify potential new prognostic risk factors predicting occult metastatic retroperitoneal lymph node disease.

RECENT FINDINGS

In accordance with the primary goal to improve quality of life, to protect fertility and to reduce long-term toxicity in survivors of testicular cancer, the major advantage of surveillance protocols is that adjuvant therapy will be administered only to those patients who require therapy. This advantage has to be balanced against a constant psychological threat and a relapse rate of 20-25% necessitating extensive polychemotherapy. Primary nerve-sparing retroperitoneal lymph-node dissection has diagnostic and therapeutic capabilities in low-volume disease; as local relapses are extremely rare, an effective and cost-saving follow-up concentrating on pulmonary recurrences can be initiated. Nerve-sparing retroperitoneal lymph node dissection represents the initial approach for mature teratomas; patients with purely embryonal carcinoma have a high risk for systemic relapses and might be better served by primary chemotherapy. The advantages of nerve-sparing retroperitoneal lymph-node dissection have to be balanced against surgery-related complications, which develop in about 17% of the patients. With regard to prognostic risk factors, the percentages of embryonal carcinoma and vascular invasion remain the most significant predictors for lymph node metastases.

SUMMARY

Surveillance and primary nerve-sparing retroperitoneal lymph-node dissection result in the same high cure rate (approaching 100%). The advantages and disadvantages of both treatment modalities must be discussed extensively with the patient, and it will be basically his decision as to which therapeutic approach is chosen.

Role of P53 and MDM2 in treatment response of human germ cell tumors

PURPOSE

Testicular germ cell tumors (TGCTs) of adolescents and adults are very sensitive to systemic treatment. The exquisite chemosensitivity of these cancers has been attributed to a high level of wild-type P53.

MATERIALS AND METHODS

To clarify the role of P53 in treatment sensitivity and resistance of TGCTs, we performed immunohistochemistry and Western blotting analysis on a series of 39 fresh-frozen primary TGCTs before therapy (unselected series). In a series of formalin-fixed paraffin-embedded TGCTs of patients with fully documented clinical course, including treatment-sensitive (n = 17) and -resistant (n = 18) tumors, P53 status was assessed by immunohistochemistry and mutation analysis. In addition, the involvement of MDM2, a P53 antagonist, was investigated by immunohistochemistry, reverse transcriptase polymerase chain reaction, and in situ hybridization.

RESULTS

Immunohistochemistry demonstrated absence of staining for P53 in 36%, 41%, and 17% of the unselected, responding, and nonresponding TGCTs, respectively. Of the positive TGCTs, most tumors, ie, 49%, 41%, and 33%, showed 1% to 10% positive nuclei. This overall low level of P53 was confirmed by Western blotting. Mutation analysis revealed only one silent P53 mutation in one of the responding patients. All embryonal carcinomas were homogeneously positive for MDM2, encoded by the full length mRNA, while a heterogeneous pattern was found for the other histologic components. Amplification of MDM2 was detected in one out of 12 embryonal carcinomas.

CONCLUSION

Although our results are in line with previous findings of the presence of wild-type P53 in TGCTs, they show that a high level of P53 does not relate directly to treatment sensitivity of these tumors, and inactivation of P53 is not a common event in the development of cisplatin resistance.